Nowadays, the commercially available touch screens are classified into several types, including a resistive touch screen, an acoustic wave touch screen, an infrared touch screen and a capacitive touch screen. When an external force is exerted on the resistive touch screen, a voltage is generated and a command is recognized according to the voltage. Moreover, acoustic waves or infrared rays pass over the surface of the acoustic wave touch screen or the infrared touch screen. By touching the surface of the acoustic wave touch screen or the infrared touch screen, the travelling path of the acoustic wave or the infrared ray is blocked and thus the corresponding command is recognized. When the human body is contacted with the capacitive touch screen, the capacitance value of the touch point of the capacitive touch screen is subjected to a change. According to the change of the capacitance value, the position of the touch position is recognized. In views of the touch accuracy and the fabricating cost, the capacitive touch screen is widely adopted.
For complying with the utilized function of the capacitive touch screen, a capacitive touch pen is introduced into the market. Hereinafter, the structure of a conventional touch pen will be illustrated with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view illustrating a conventional touch pen. A conductive rubber tip 11 of the conventional touch pen 1 is used as a contact terminal. The conductive rubber tip 11 is sheathed around a fixing post 13, which is contacted with a metallic pen tube 12. Consequently, the conductive rubber tip 11 and the metallic pen tube 12 are combined together. When the conductive rubber tip 11 touches the capacitive touch screen, the electric energy of the human body is transmitted to the conductive rubber tip 11 through the metallic pen tube 12 and the fixing post 13. Consequently, the capacitance value of the touch point between the capacitive touch screen and the conductive rubber tip 11 is changed. According to the change of the capacitance value, a position of the touch point can be accurately judged by the capacitive touch screen.
However, if the diameter of the conductive rubber tip 11 is smaller than 5 mm, the contact area is very small. Under this circumstance, the capacitive touch screen fails to accurately realize the position of the touch point. For preventing the small conductive rubber tip from causing the poor sensing problem, the diameter of the current conductive rubber tip is usually in the range between 5 mm to 8 mm. Since the larger conductive rubber tip may hinder the line of vision of the user, it is difficult for the user to precisely perform the touch control.
Therefore, it is an important issue to reduce the contact terminal of the capacitive touch pen with respect to the capacitive touch screen while allowing the capacitive touch screen to accurately judge the position of the touch point.